In history, the early modern period of modern history follows the late Middle Ages of the post-classical era. Although the chronological limits of the period are open to debate, the timeframe spans the period after the late portion of the post-classical age (c. 1500), known as the Middle Ages, through the beginning of the Age of Revolutions (c. 1800) and is variously demarcated by historians as beginning with the Fall of Constantinople in 1453, with the Renaissance period, and with the Age of Discovery (especially with the discovery of America by Christopher Columbus in 1492, but also with the discovery of the sea route to the East), and ending around the French Revolution in 1789. Historians in recent decades have argued that from a worldwide standpoint, the most important feature of the early modern period was its globalizing character. The period witnessed the exploration and colonization of the Americas and the rise of sustained contacts between previously isolated parts of the globe. The historical powers became involved in global trade. This world trading of goods, plants, animals, and food crops saw exchange in the Old World and the New World. The Columbian exchange greatly affected the human environment.